Transcriptome Sequencing and Differential Expression Analysis of Ovaries from Kazakh Mares During Seasonal Quiescence and Estrus Activation

Abstract

Simple Summary Kazakh horses are typical seasonal breeders, and their reproductive activity is strongly influenced by seasonal environmental changes. During the non-breeding season, ovarian activity is markedly reduced. Hormonal treatment can induce an ovarian response during this period, but the associated early molecular changes remain incompletely understood. In this study, we compared ovarian gene expression between non-hormonally stimulated seasonally quiescent mares and mares showing ovarian activation following cloprostenol and eCG treatment during the same seasonal anestrous period. Numerous differentially expressed genes were associated with immune regulation, metabolic processes, and reproductive functions. C1QB, CREB5, and IRS1 were highlighted as transcriptomic candidate genes based on their differential expression and association with relevant biological pathways; however, their functional roles were not tested in this study. Importantly, the hormonally induced group does not represent the natural transition to breeding-season reproductive activity or a stable natural estrous state. The observed transcriptional differences may therefore reflect both ovarian functional responses and direct or indirect effects of hormonal treatment. These findings should be considered a basis for further hypothesis-driven studies rather than evidence of specific molecular mechanisms controlling natural seasonal reproduction.